1. Field of the Invention
This invention relates to blades, as used to clean conveying belts and, more particularly, to a tensioning assembly for urging the cleaning blade against a conveying belt.
2. Background Art
Endless belts are used in a wide range of environments to convey different articles and materials. Often particulate material is conveyed on belts between loading and discharge locations. At the discharge location, the material separates from the belt for collection, as for use or disposal, or for transportation to yet another location.
In certain environments, conveyed materials are, or become, wet so that they tend to adhere to the conveying belt surfaces. The material may be deposited on the conveying belt in a dampened state. Alternatively, dry material may become dampened by reason of being deposited on a conveying belt that has moisture thereon or by reason of the system's being operated in rainy and/or humid conditions. Over time, adhered materials tend to accumulate on the conveying belts. If these materials are not removed, the progressive accumulation may ultimately detrimentally affect the system operation.
The dampened material accumulated to any significant extent may add a significant amount of weight to the belts as they are continuously advanced in an endless path. This places an additional strain on the drive system, and support structure, for the conveying belts. The accumulation of significant quantities of foreign material may also produce an undesired deformation of the belts which may affect how they operate. In some environments, additional weight may cause deformation, or in a worse case failure, of the conveying belts, which may necessitate system adjustments and/or adjustments to, or replacements of, the conveying belts.
To mitigate the above problems, it is known to use cleaning blades at different locations to scrape foreign matter from the advancing belts. These conveying belts vary widely in terms of construction and size. A single blade may be used to span the full width of a conveying belt. Alternatively, a plurality of cleaning blades may be used across the width of the belt, and may be staggered lengthwise to redundantly engage a part of the width of the belt.
The cleaning blades are designed to perform optimally when borne against belt surfaces with a specific pressure. As the conveying systems are operated, there is a progressive wearing away of the surfaces of the cleaning blades that contact the belts. Thus, to maintain optimal pressure by the blades on the conveying belts, it may become necessary to periodically adjust the system that urges the blades against the belts.
Various systems have been devised to bias the cleaning blades against the conveying belts. A common design for such tensioners utilizes a torsion loading mechanism that produces the required blade bias. An exemplary system is shown in U.S. Pat. No. 6,056,112. These systems typically incorporate a fixed frame relative to which an assembly is turned around an axis to develop the blade bias. Once the desired bias is generated, it is known to install a pin, or the like, to fix the assembly relative to the frame. Different openings register to receive the pins with different blade biases set.
While these systems perform effectively, they inherently have some associated inconveniences. The operator must turn the assembly to produce the bias as through a tool, such as a wrench. If the system adjustments are carried out by a single individual, the individual must effect the turning and insert the pin with the desired blade pressure applied. As the wrench is turned, a progressively increasing resistance force is encountered. Continued turning causes a stored force to be generated that tends to release the pressure on the blade. If care is not taken, this restoring force may cause the turning tool to be moved in a manner that might cause it to detrimentally contact the operator. Inherently, the maintenance of a force on the blade and the insertion of a pin, or the like, is awkward for a single individual. Several adjustments may have to be made through a trial and error process to ultimately effect the appropriate adjustment.
It is also known to use ratchet arrangements to facilitate loading of a blade against a conveying belt and potentially eliminates the above problem. Typically, these ratchet systems are made with metal components. In many environments, the tensioning systems will be exposed to moisture and chemicals that may cause rust and corrosion. This may impair the operation of the tensioning systems, potentially necessitating repair and, in a worst case, replacement. This could lead to expensive down time in certain systems, particularly those in which long, continuous, conveying expanses are utilized in which the entire line must be shut down to effect maintenance of the tensioning system on any portion thereof.